In this example, we see that LUN 1 contains 8 bad blocks. To list the the bad blocks, we will use a -w (followed by LUN number) switch in the raidtool utility and to clear the lost blocks, we will use the -W (followed by LUN number).

Very nice short and to the point article to list and clear the lost blocks. But after listing the lost blocks, how to verify if the lost blocks had data in it or those blocks were empty to begin with? What exactly clear bad blocks do? (i believe it will just write 0s and clear any data if there were some). Is there a better way to make sure i am not clearing data which could be recovered somehow otherwise?